Flow control apparatus

ABSTRACT

Oxygen gas admission into a breathing atmosphere is controlled by means of a flow control unit. A small quantity of the input oxygen gas is discharged through a discharge orifice against the edge surface of a disc forming part of an electric galvanometer movement. A partial pressure of oxygen sensor in the breathing atmosphere provides an output signal to the galvanometer movement to move the disc. Movement of the disc with respect to the discharge orifice changes the back pressure sensed at the flow control unit to govern the admission of new gas.

United States Patent 91 Fleischmann FLOW CONTROL APPARATUS Lewis W. Fleischmann, Randallstown, Md.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Mar. 25, 1970 [21] App]. No.: 22,476

[75] Inventor:

[52] US. Cl 128/142, 137/82, 137/489 [51] Int. Cl A62b 7/02, Fl6k 31/12 [58] Field of Search 137/88, 101.21, 63 R, 81, 95,

[56] References Cited UNITED STATES PATENTS 3,129,719 4/1964 Mollick 137/489 3,113,582 12/1963 3,256,740 6/1966 3,258,025 6/1966 Howland 137/85 11] 3,788,310 Jan. 29, 1974 3,019,804 2/1962 Miller 137/81 3,223,102 12/1965 Kies 137/82 3,051,192 8/1962 Fagot 137/82 3,127,891 4/1964 Henneman 128/144 Primary ExaminerMartin P. Schwadron Attorney, Agent, or FirmD. Schron [57] ABSTRACT 9 Claims, 14 Drawing Figures PATENTED 3,788,310

SHEU 1 F 4 22 MOVEMENT UNIT 23 f H FIG. I SOURCE FLOW OF 'fi CONTROL 63? TO SYSTEM FLUID UNIT IOJ p0 ATMA Q FIG. 3

WITNESSES INVENTOR W 45 Lewis W. Fleischmcmn 1 FLOW CONTROL APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention in general relates to fluid flow control apparatus and particularly to life support equipment wherein the fluid is oxygen.

2. Description of the Prior Art Breathing systems which provide a respirable atmosphere are utilized in various fields such as diving, outer space, and medical applications, to name a few. In such systems control of the oxygen supply is of primary importance and oxygen requirements vary according to the ambient pressure and the task being performed.

A widely used system is one wherein oxygen is admitted in a manner to maintain the partial pressure of oxygen within a prescribed range. A typical system might include a partial pressure of oxygen sensor which provides an output signal and an electrically operated solenoid valve which is responsive to the sensor signal for opening, and admitting oxygen into the breathing atmosphere. An amplifier is generally required to amplify the sensor signal to the operating level of the solenoid. For outer space applications it would be desired to have the control for admitting oxygen as small as possible so that the payload of the carrying vehicle can be increased.

For underwater work, as in space applications, it is very often desired to reduce the weight of equipment utilized. For example in closed circuit breathing apparatus carried by a diver a typical system requires the use of auxiliary electrical power to run both the amplifier and the solenoid valve. The valve consumes approximately 4 watts of power while the amplifier consumes approximately 3.6 watts and accordingly a battery pack is required. This battery pack requirement utilizes space, adds weight and necessitates field service by way of recharging.

SUMMARY OF THE INVENTION Basically, the present invention allows for the introduction of a fluid such as oxygen into a system in a proportional manner with or without the use of auxiliary battery equipment and includes a flow control means which is connectable with a source of the oxygen and to which is connected passageway means and a discharge orifice which discharges a small quantity of the fluid against a surface. A sensor provides an output signal as a function of some parameter of the fluid, for example partial pressure of oxygen and the output signal is utilized for relatively moving the discharge orifice and the surface to vary the back pressure at the flow control means. The flow control means therefore is responsive to this relative movement for controlling the flow of the gas into the system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a block diagram of the present invention;

FIG. 2 illustrates, partially in section, one embodiment of the present invention;

FIG. 3 is a top view of the instrument illustrated in FIG. 2;

FIGS. 4 and SQshow respective top and bottom views of the disc portion of the instrument illustrated in FIG.

FIG. 6 illustrates the orientation of the disc with respect to external magnets;

FIG. 7 illustrates the disc of FIG. 2 in two different positions during operation;

FIGS. 8 and 8A are sectional views of a discharge nozzle adjacent two different surfaces;

FIGS. 9 through 12 illustrate different embodiments of the movement unit of FIG. 1;

FIG. 13 is a representation of a closed circuit underwater breathing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a flow control means in the form of flow control unit 10 receives at input 12 a fluid from source 14 and is operable to control the flow of fluid at output 16 for introduction of the fluid into a system. Sensor means in the form of sensor 20 is operable to sense a predetermined component of the fluid in the system to provide a corresponding output signal related to that component. A small quantity of the input fluid is provided to movement unit 22 along fluid passage 23. The fluid discharging from fluid passage 23 strikes a surface, with the discharge portion of fluid passage 23 and the surface having a relative positioning. The movement unit is responsive to the output signal from the sensor 20 to vary the relative positioning and in so doing, vary the back pressure at flow control unit 10 to close or proportionally open a valve within the flow control unit for controlling fluid flow. The invention, by way of example, will be described with respect to a breathing system wherein the controlled fluid is oxygen and wherein the component sensed is the partial pressure of oxygen in the system. One such example is illustrated in FIG. 2.

Components of FIG. 2 identifiable in FIG. 1 have been given like reference numerals. Input 12, which may be a gas fitting, is connectable with a source of oxygen under pressure and input oxygen enters into cavity 25. The apparatus described herein may also be used for an input helium-oxygen mixture. Cavity 28 communicates with the system ambient atmosphere by means of output 16 and is at system pressure, which for the case of underwater breathing apparatus, will be the pressure of the gas supplied to the user for breathing. Separating the cavities 25 and 28 is a tilt valve 30 having a stem 31 urged to a closed position against seat 32 by means of spring 35 to close valve passage 36.

The stem portion 31 of tilt valve 30 bars against diaphragm member 37 which is movable against the stem 31 when the pressure in upper diaphragm chamber 39 is greater than the pressure in lower diaphragm chamber 40 by a certain amount. Input oxygen flows from cavity 25 into cavity 28 and the system atmosphere upon movement of the stem 31 and the greater the movement, the greater the amount of oxygen admitted.

By means of second fluid passage 42 a small quantity of input oxygen bypasses the tilt valve 30 and enters the first fluid passage 23, which may be in the form of tubing. Alternatively, the first fluid passage may be supplied by a source other than the input. In order to control and keep constant the mass rate of flow of bypass oxygen into the line 23 there is provided flow restrictor means within the fluid passage 42. The flow restrictor means is in the form of an orifice 44 and if different mass flow rates are desired, different size orifices may be inserted, or alternatively, the orifice may be made variable such as by the provision of a needle valve. In order to insure that the mass flow rate is constant it is preferable that the oxygen be supplied at a pressure which is approximately twice that of the ambient atmosphere.

The bypass oxygen in fluid passage 23 exits through a discharge orifice 50 held in position by a ring member 52 and which is disposed adjacent a surface 55 to define a gap 56 therebetween. The discharge orifice 50 and the surface 55 are movable relative to one another for varying the size of the gap and in the embodiment of FIG. 2 the discharge orifice 50 is fixed and the surface 55 is movable. A plan view of the arrangement, with certain parts omitted for clarity, is illustrated in FIG. 3 to which additional reference should be made. The surface 55 is the peripheral surface of a disc 58, constituting a rotary armature or movable member of an electric indicating instrument. The armature 58 is pivoted between two jewel bearings 60 and 61 by means of posts 63 and 64 although taunt band or other arrangements are possible. A source of electrical current is applied to input terminals 68 and 69 connected to the windings of the armature by means of upper and lower spiral springs 72 and 73.

FIGS. 4 and illustrate respective top and bottom views of the armature 58. In FIG. 4 the terminal 68 is connected through the spiral spring 72 to windings 75 which may be affixed to, etched on, or embedded in the armature 58. Winding 75 traverses the disc at point 77 and continues on the other side of the disc as seen in FIG. 5 where the winding is designated 75 and is connected to terminal 69 through spiral spring 73. The armature 58 is placed in a magnetic field established by magnets 80, 81, as illustrated in FIG. 6 and application of a current to the windings results in a deflecting torque which rotates the armature 58 proportionally. Upon the removal of the current, the spiral springs provide a restoring torque. Such operation is well known to those skilled in the art and the indicating instrument herein may be a modified galvanometer.

Referring once again to FIGS. 2 and 3, the input terminals 68 and 69 of the instrument movement are connected by means of leads 83 and 84 to the sensor which for the present example is a partial pressure of oxygen sensor operable to provide an output signal on leads 83, 84 in response, and in proportion to the partial pressure of oxygen in the atmosphere being monitored. Although a small battery may, if desired, be provided for operation of the sensor 20, it is preferable that te sensor be constructed such that it is self biasing. Such sensors are known to those skilled in the art, and one such sensor is described in US. Pat. No. 3,410,778.

An output signal on leads 83 and 84 from the sensor 20 causes the armature 58 to rotate. If the armature 58 pivoted, that is rotated about its central axis then the gap 56 would never vary. Accordingly the instrument movement is modified so that the armature 58 pivots about a point P displaced from the geometric center C of the armature by a slight amount. Point P is actually the rotational axis viewed in plan. Pointer 86 used for obtaining a readout on scale 87 is of a weight to counterbalance the offset in the armatures center of gravity, thereby maintaining a statically balanced assembly. With the pivot point displaced from the center point, the gap 56 will vary as the armature 58 is rotated and the gap distance will be a function of the sensor output.

In order to prevent the discharging gas from turning the disk 58 as by turbine action, the longitudinal central axis L of the discharge orifice 50 passes through the rotational axis of the disc 58.

FIG. 7 illustrates, to an exaggerated scale, the relationship between armature rotation and gap distance. The pivot point P of the armature 58 is displaced by a distance d from the geometric center C of the armature. The distance d may be in the order of 0.0015 to 0.002 inch. The armature 58, shown in solid line, is in a position where the gap 56 is a minimum, with the gap distance x being approximately 0.0002 to 0.0004 inches. At full scale deflection, shown dotted, center C will have rotated about pivot point P such that the gap has a greater width of x where x may be approximately 0.001 inch. With increasing current from the sensor the gap progressively widens until it reaches its maximum of x and conversely a decreasing current causes the gap to reduce towards its minimum x.

In FIG. 8 there is illustrated the discharge orifice 50 adjacent a surface S with exiting gas from fluid passage 23 being indicated by the streamlines 90. As long as the distance between the end of the discharge orifice 50 and the surface S is approximately of magnitude G or less, then relative movement of the discharge orifice and surface towards one another will cause a back pressure, that is, a pressure signal, within the fluid passage 23, and the pressure signal will be proportional to the square of the gap distance. If the surface S is irregular or is inclined with respect to the discharge orifice then at any instant of time the gap distance may be defined as the average distance between the discharge orifice and the surface. The critical value of G is dependent upon the flow rate of discharge gas. At gap distances greater than G, relative movement of the orifice and surface toward or away from one another will have no effect on the pressure within the line 23. The apparatus of the present invention is designed to maintain the gap distance within this critical value G.

FIG. 8A illustrates another surface which will provide a varying pressure signal when moved relative to discharge oirifice 50. The surface S which is relatively movable in the direction of the arrows, includes a step portion S which traverses the discharge orifice and in so doing will vary the back pressure in fluid passage 23 in accordance with the amount of orifice traversed.

The effect of the back pressure may be demonstrated with reference to FIg. 2. By way of illustration let it be assumed that the surface 55 of armature 58 is not prescut and that the discharge aperture 50 discharges gas to the surrounding ambient medium. Further assuming negligible or zero pressure drop in fluid passage 23, the pressure within the upper diaphragm chamber 39 will be equal to the ambient pressure at the discharge orifice 50. Since the gas outlet 16 communicates with the ambient medium, the pressure within the lower diaphragm chamber 40 is also equal to the pressure of the ambient medium, and valve 30 remains in a closed position. With the discharge orifice 50 adjacent the surface 55 and with a maximum width gap, there will be a small back pressure which will be reflected back to diaphragm chamber 39 as a pressure signal. The increase in pressure however is not enough to overcome the spring stiffness associated with the diaphragm member 37 and spring 35 (through the tilt valve 30) and the tilt valve 30 remains in its closed position.

At the other extreme, with the smallest gap, fluid passage 23 is almost blocked at its output and the pressure within the diaphragm chamber 39 will build up to substantially the pressure of the gas supplied at input 12. Since the input pressure is much greater than the ambient pressure in the lower diaphragm chamber 40, the diaphragm member 37 is moved downwardly against the stem 31 causing it to tilt off of seat 32 to open the valve and allow passage of input gas into output cavity 28 and into the ambient medium through the output 16. Intermediate the extremes of maximum and minimum gap distance, the back pressure, or pressure signal, will be of a value to cause a proportional movement of the stem 31 and a proportional opening and admittance of gas into the system.

Let it be assumed that for a particular operation the user desires a system atmosphere having a partial pressure of oxygen equal to 1.0 atmospheres absolute. The flow restrictor means 44 is chosen or set to preferably pass at least a quantity of oxygen equal to the number of personnel breathing the system atmosphere times the minimum metabolic amount of oxygen needed to survive. For one person the flow rate would be approximately 0.3 liters per minute. In this manner, should a failure occur, life supporting oxygen would still be placed in the system.

By way of initial calibration the sensor 20 may be put into a known calibration gas, such as an atmosphere of IOO'percent oxygen at 1 atmosphere pressure and its output signal therefore will be the equivalent of a scale reading of 1.0. The scale 87 is moved relatively so that the pointer 86 lines up with a reading of 1.0. With the sensor 20 still in the calibration gas, xygen may be admitted at the input 12 of servo valve and means, such as a flowmeter, may be connected to the output 16 to detect any output flow. If there is an output flow, knob 93 is manually rotated causing rotation of the ring member 52. Since the discharge orifice 50 is carried by the ring member 52 the rotation has the effect of varying the gap distance. With the sensor still in the calibration gas its output signal is constant and the armature 58 does not move. Knob 93 is rotated until the gap 56 increases thus reducing the back pressure in upper diaphragm chamber 39. Rotation of the knob 93 is continued until tilt valve just closes, as evidenced by a zero flow at the output 16. If the gap 56 was initially too large then the knob 93 may be rotated to decrease the gap until an output flow is detected and thereafter rotated in an opposite direction to slightly increase the gap to attain a zero flow condition as previously described.

With this initial calibration the apparatus may be placed into a system, the atmosphere of which is to be maintained at a partial pressure of 1.0. When placed in such atmosphere, (and now the sensor is no longer in the calibration gas) and if in fact tha partial pressure is 1.0 the armature 58 will not move from its initial position and the tilt valve 30 will remain closed. If the partial pressure of oxygen should decrease below the set 1.0 value the output signal provided by the sensor 20 will cause rotation of the armature 58 to narrow the gap 56 to cause a pressure buildup in upper diaphragm chamber 39 and an opening of tilt valve 30 to cause the addition of oxygen into the system. The greater the difference between the desired and actual partial pressure of oxygen the greater will be the opening of the tilt valve 30. Oxygen is added to the system atmosphere until the sensor senses a 1.0 value which causes a return of the armature to its initial position and a cutting off of additional oxygen at the output 16.

In actuality the oxygen is breathed by the user or users and the tilt valve 30 remains continuously open to supply additional oxygen to the system. Operation is like a closed loop feedback system in that as oxygen is consumed the partial pressure reduces and the sensor 20 provides an output signal which tends to rotate the armature 58 to lessen the gap 56. A reduction in gap distance causes downward movement of the diaphragm member 37 to open the tilt valve which introduces more oxygen into the sytem. The increased oxygen increases the partial pressure and the sensor output tends to return the armature 58 to its initial position. The net effect of this feedback loop operation is to maintain the tilt valve 30 open to a position where oxygen is added continuously as it is being breathed. For example if the user burns 2 liters of oxygen per minute and oxygen is discharged to the system at a rate of 0.3 liters per minute through orifice 50 the tilt valve 30 opens to allow an output of 1.7 liters of oxygen per minute. If the user works harder more oxygen is burned, the partial pressure of oxygen reduces and the net effect is to open the valve more to allow a greater flow of oxygen into the system. With the flow control unit 10 tending to supply oxygen continuously as the oxygen is being used, there is assured a more homogenous mixing of oxygen gas with the inert gas making up the rest of the atmosphere. With an electrically operated solenoid a much larger quantity of oxygen than the demand requires is admitted with a possibility of oxygen clouds or pockets forming.

If a different value of partial pressure of oxygen atmosphere is desired the apparatus may be recalibrated with a different calibration gas. Not only does ring 52 and knob 93 serve as a means for intially positioning the discharge orifice but in addition, a change may be made after an initial calibration for one value by turning the knob 93 until the pointer 86 moves to another desired setting.

In some situations the user may desire to admit a gross amount of oxygen to the system and independent of the back pressure provided by the orifice armature positioning. For this purpose a maximum pressure signal is provided to the flow control unit 10 by means such as, a purge valve 96 whereby depressing button 97 causes pad 99 at the end of rod to close off the lower portion of fluid passage 23 connected to the flow control unit 10. This closing off of the passage results in a pressure buildup within upper diaphragm chamber 39 to open the tilt valve 30. After purging, the button 97 is released and admission of oxygen is thereafter controlled as previously described.

From the foregoing it may be seen that the gap distance determines the back pressure which governs the amount of oxygen added and therefore the partial pressure of oxygen in the system. The sensor output signal is proportional to this partial pressure and is utilized for scale deflection of the pointer. A certain gap distance therefore corresponds to a certain partial pressure and a certain scale deflection. If the gap distance was directly proportional to the back pressure then for equal increments of gap distance the scale 87 could be of proportionally equal increments. It will be remembered however that the back pressure is proportional to the square of the gap distance and accordingly for the circular armature 58 the scale 87 would be non-linear in accordance with a parabolic function of increment spacing. Alternatively a linear scale may be utilized if the surface 55 f the armature 58 has a parabolic shape.

With respect to the shape of the armature 58, it has been assumed that the output of sensor 20 is linear over the entire operating range. If in fact the output is not linear then the armature 58 may be additionally shaped to accommodate for such non-linear output.

In FIG. 3 (and in FIG. 7) the pivot point P is displaced from the geometric center of the armature disc 58. In FIG. 9 there is illustrated an armature 103 wherein the pivot point P is situated at the geometric center C. To provide a variable gap 105 between the discharge orifice 50 and the armature 103, there is provided on the periphery of the armature an extension 107 which may be an integral part of, or added to the armature 103. To provide balance, an extension 107' is positioned diametrically opposite extension 107.

FIGS. 10 and 11 illustrate another form of galvanometer movement wherein the output from a sensor is provided to windings 110 rotatable in a magnetic field and carrying a segment 112 disposed at a slight angle as 2 seen in FIG. 11. Gas is discharged from the discharge orifice against the top surface of the segment 112 and the angular orientation thereof provides a variable gap as windings rotate. A balancing segment 112' is provided and is angularly oriented by the same degree in an opposite direction. As was the case with respect to FIG. 3, the surfaces of FIGS. 9 and 10 may be varied to compensate for non-linearity or to provide any desired flow pattern.

FIG. 12 illustrates another form of movement unit. Discharge orifice 50 is positioned adjacent to a transducer structure 117 affixed in a manner that its end 118 moves in the direction of either arrow upon the application of an input signal to electrodes 120 and 121. The degree of movement, and accordingly the gap distance varies in accordance with the magnitude of signal applied. Such arrangement can be utilized where amplifier apparatus can be tolerated. The output signal from sensor 20 is applied to an amplifier means 23 to increase the sensor signal to the proper level for operation of the transducer structure.

The present invention finds applicability in a wide variety of underwater, surface and extra terrestrial systems, particularly life support breathing systems. One such system is illustrated in FIG. 13 which is representative of a diver worn, closed circuit underwater breathing apparatus. 7

Components described in FIGS. 2 and 3 are utilized in the apparatus of FIG. 13 and have been given the same reference numeral. The breathing apparatus includes passageway means having a diver mouthpiece 132 by which the diver inhales breathing gas from flexible inhalation breathing bag 134 and exhales into flexible exhalation breathing bag 135.

The inhalation and exhalation breathing bags 134 and 135 are additionally connected to a canister 137 having a carbon dioxide absorbent 139 contained herein. An inert gas, generally helium, is supplied from high pressure helium source 142 to the inhalation breathing bag 134 and is supplied at the ambient pressure by the provision of first and second stage reducing regulators 143 and 144.

Oxygen is admitted to the system from the high pressure oxygen source 145 through the flow control unit 10. Connected at the output 16 of flow control unit 10 is a diffuser member 147.

The partial pressure of oxygen is sensed in the inhalation breathing bag 134 by means of sensor 20 which provides an output signal to the indicating instrument 51 which transmits a pressure signal along fluid passage 23 to the flow control unit 10 to control the admission of more oxygen as it is used by the diver. The instrument 51 could be located on the divers wrist to additionally serve as a read-out, in which case the fluid passage 23 may be capillary tubing running up the divers arm and to the canister 137 in such a manner as to prevent pinching thereof to prevent false pressure signals. Alternatively two sensors and two instruments could be provided, one instrument being positioned on the divers wrist for indicating purposes and connected to one sensor, and the other instrument, shown dotted within the canistor 137 being connected to the second sensor shown dotted, for control purposes.

I claim:

1. Apparatus for introducing a fluid into a system, comprising:

a. flow control means having an input, connectable with a source of said fluid, and an output;

b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage;

c. first means for supplying said discharge orifice with a fluid for discharging;

d. a surface positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance with the relative positioning of said surface and said discharge orifice;

e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid;

f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal;

g. said flow control means being responsive to said pressure signal for governing flow of said fluid;

h. said surface including a step portion; and

i. said step portion traversing said discharge orifice as said surface and said discharge orifice are relatively moved.

2. Apparatus for introducing a fluid into a system,

comprising:

a. flow control means having an input, connectable with a source of said fluid, and an output;

b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage;

c. first means for supplying said discharge orifice with a fluid for discharging;

d. a surface positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance wth the relative positioning of said surface and said discharge orifice;

e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid;

f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal;

g. said flow control means being responsive to said pressure signal for governing flow of said fluid;

h. a second fluid passage connecting said first fluid passage with said input, whereby said fluid for discharging is provided by said source of fluid;

. flow restrictor means within one of said fluid passages for providing a predetermined rate of discharge of said fluid for discharging and wherein; j. said fluid includes oxygen; and k. said flow restrictor means is of a size to provide a rate of discharge of oxygen at least equal to the minimum necessary metabolic rate of consumption of oxygen by a user.

3. Apparatus for introducing a fluid into a system,

comprising:

a. flow control means having an input, connectable with a source of said fluid, and an output;

b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage;

c. first means for supplying said discharge orifice with a fluid for discharging;

d. a surface positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance with the relative positioning of said surface and said discharge orifice;

e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid;

f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal;

g. said flow control means being responsive to said pressure signal for governing flow of said fluid; and

h. means for providing said flow control means with a maximum pressure signal independent of the relative positioning of said surface and said discharge orifice.

4. Apparatus according to claim 3 wherein a. said means is a purge valve operable upon activation to close off said first fluid passage.

5. Apparatus for introducing a fluid into a system,

comprising:

a. flow control means having an input, connectable with a source of said fluid, and an output;

b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage;

c. first means for supplying said discharge orifice with a fluid for discharging;

d. a surface positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance with the relative positioning of said surface and said discharge orifice;

e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid;

f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal; g. said flow control means being responsive to said pressure signal governing flow of said fluid;

5 h. said movement means including an electric current indicating instrument for receiving the output signal of said sensor means and having a circular disc rotatable about a rotational axis in response to said output signal;

i. said rotational axis being displaced from the central axis of said disc; and

j. said surface being defined by the peripheral wall portion of said disc.

6. Apparatus according to claim 5 wherein:

a. said discharge orifice has a longitudinal central axis, and wherein b. said longitudinal central axis intersects said rotational axis. 9

7. Apparatus according to claim 5 which includes:

a. means for manually positioning and changing position of said discharge orifice relative to said peripheral wall portion of said disc.

8. Apparatus for introducing oxygen containing gas into a life support breathing system, comprising:

a. flow control means having an input, connectable with a source of said gas, and an output;

b. a discharge orifice operatively connected with said flow control means by means of a first gas passage;

0. first means for supplying said discharge orifice with a gas for discharging;

d. a surface positioned adjacent to said discharge ori fice for providing a pressure within said gas passage in accordance with the relative positioning of said surface and said discharge orifice;

e. sensor means operable to provide an electrical output signal indicative of the partial pressure of oxygen within said system;

f. movement means responsive to said electrical output signal for relatively moving said surface and said discharge orifice as a function of said output signal; and

g. said flow control means being responsive to said pressure signal for governing introduction of said oxygen containing gas into said system.

9. Apparatus according to claim 8 wherein the apparatus is diver worn underwater breathing apparatus and which includes:

a. flexible breathing bag means;

b. means for communicating said breathing bag means with a diver;

c. carbon dioxide arsorbent means connected in circuit between said breathing bag means;

(1. means for introducing an inert gas into said system;

e. a source of oxygen containing gas;

f. said flow control means being connected to said source of oxygen containing gas. 

1. Apparatus for introducing a fluid into a system, comprising: a. flow control means having an input, connectable with a source of said fluid, and an output; b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage; c. first means for supplying said discharge orifice with a fluid for discharging; d. a surface positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance with the relative positioning of said surface and said discharge orifice; e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid; f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal; g. said flow control means being responsive to said pressure signal for governing flow of said fluid; h. said surface including a step portion; and i. said step portion traversing said discharge orifice as said surface and said discharge orifice are relatively moved.
 2. Apparatus for introducing a fluid into a system, comprising: a. flow control means having an input, connectable with a source of said fluid, and an output; b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage; c. first means for supplying said discharge orifice with a fluid for discharging; d. a surfacE positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance wth the relative positioning of said surface and said discharge orifice; e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid; f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal; g. said flow control means being responsive to said pressure signal for governing flow of said fluid; h. a second fluid passage connecting said first fluid passage with said input, whereby said fluid for discharging is provided by said source of fluid; i. flow restrictor means within one of said fluid passages for providing a predetermined rate of discharge of said fluid for discharging and wherein; j. said fluid includes oxygen; and k. said flow restrictor means is of a size to provide a rate of discharge of oxygen at least equal to the minimum necessary metabolic rate of consumption of oxygen by a user.
 3. Apparatus for introducing a fluid into a system, comprising: a. flow control means having an input, connectable with a source of said fluid, and an output; b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage; c. first means for supplying said discharge orifice with a fluid for discharging; d. a surface positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance with the relative positioning of said surface and said discharge orifice; e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid; f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal; g. said flow control means being responsive to said pressure signal for governing flow of said fluid; and h. means for providing said flow control means with a maximum pressure signal independent of the relative positioning of said surface and said discharge orifice.
 4. Apparatus according to claim 3 wherein a. said means is a purge valve operable upon activation to close off said first fluid passage.
 5. Apparatus for introducing a fluid into a system, comprising: a. flow control means having an input, connectable with a source of said fluid, and an output; b. a discharge orifice operatively connected with said flow control means by means of a first fluid passage; c. first means for supplying said discharge orifice with a fluid for discharging; d. a surface positioned adjacent to said discharge orifice for providing a pressure signal within said fluid passage in accordance with the relative positioning of said surface and said discharge orifice; e. sensor means operable to provide an output signal as a function of a predetermined parameter of said fluid; f. movement means responsive to said output signal for relatively moving said surface and said discharge orifice as a function of said output signal; g. said flow control means being responsive to said pressure signal governing flow of said fluid; h. said movement means including an electric current indicating instrument for receiving the output signal of said sensor means and having a circular disc rotatable about a rotational axis in response to said output signal; i. said rotational axis being displaced from the central axis of said disc; and j. said surface being defined by the peripheral wall portion of said disc.
 6. Apparatus according to claim 5 wherein: a. said discharge orifice has a longitudinal central axis, and wherein b. said longitudinal central axis intersects said rotational axis.
 7. Apparatus according to claim 5 which includes: a. means for manually positioning and changing position of said discharge oriFice relative to said peripheral wall portion of said disc.
 8. Apparatus for introducing oxygen containing gas into a life support breathing system, comprising: a. flow control means having an input, connectable with a source of said gas, and an output; b. a discharge orifice operatively connected with said flow control means by means of a first gas passage; c. first means for supplying said discharge orifice with a gas for discharging; d. a surface positioned adjacent to said discharge orifice for providing a pressure within said gas passage in accordance with the relative positioning of said surface and said discharge orifice; e. sensor means operable to provide an electrical output signal indicative of the partial pressure of oxygen within said system; f. movement means responsive to said electrical output signal for relatively moving said surface and said discharge orifice as a function of said output signal; and g. said flow control means being responsive to said pressure signal for governing introduction of said oxygen containing gas into said system.
 9. Apparatus according to claim 8 wherein the apparatus is diver worn underwater breathing apparatus and which includes: a. flexible breathing bag means; b. means for communicating said breathing bag means with a diver; c. carbon dioxide arsorbent means connected in circuit between said breathing bag means; d. means for introducing an inert gas into said system; e. a source of oxygen containing gas; f. said flow control means being connected to said source of oxygen containing gas. 